In accordance with advancement of industry and varied lifestyles, research into applying high-level functions such as transparency to materials is actively underway so as to realize differentiation of products. For example, research into providing transparency to materials as in a cover of a washing machine to see laundry, a dust collector of a vacuum to see how much dust is collected, a housing of a game console, transparent windows of home appliances, transparent windows of office equipment, etc. is very actively underway. However, the existing acrylonitrile-butadiene-styrene (hereinafter referred to as ABS) copolymer resin used in these components has superior impact resistance, chemical resistance, processability and surface gloss, but is opaque due to characteristics thereof, whereby use thereof in materials requiring transparency is limited.
As generally used transparent resins, there are polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, polystyrene (PS) resin, polyacrylonitrile-styrene (SAN) resin, etc. Since polycarbonate resin has superior impact strength and transparency, but poor processability, it is difficult to prepare complex products using the same. Polymethylmethacrylate resin has superior optical characteristics, but very poor impact resistance and chemical resistance. In addition, polystyrene (PS) resin and polyacrylonitrile-styrene (SAN) resin also have very poor impact resistance and chemical resistance.
Acrylonitrile-butadiene-styrene based (hereinafter referred to as ABS) terpolymers are opaque resins in which properties such as impact strength and fluidity are well balanced. U.S. Pat. No. 4,767,833, Japanese Patent Laid-Open Publication No. Hei 11-147020, European Patent NO. 703,252, and Japanese Patent Laid-Open Publication No. Hei 8-199008 disclose methods of introducing acrylic acid alkyl ester or methacrylic acid alkyl ester into an acrylonitrile-butadiene-styrene based (ABS) resin having superior impact resistance, chemical resistance, processability, etc. to provide transparency. Since these methods use emulsion polymerization, final products exhibit decreased moist-heat characteristics due to characteristics of emulsion polymerization through which a large amount of residue is generated, thus being deformed under conditions of high temperature and humidity. Accordingly, it is difficult to apply the same to products that come into contact with high-temperature water, such as humidifiers, washing machines, coffee machines, and water purifiers, and children's toy which are sterilized.
Therefore, there is an urgent need for transparent resins which can enhance moist-heat characteristics and have superior color and transparency.